The effect of non-uniformity density structure on the molecular cloud-cores magnetic braking in the ideal MHD framework

TL;DR

This study investigates how non-uniform density structures in molecular cloud cores influence magnetic braking, revealing that steeper density profiles enhance magnetic braking efficiency and significantly reduce core rotation.

Contribution

It demonstrates, through simulations, that increasing density steepness in molecular cloud cores intensifies magnetic braking effects, a novel insight into core dynamics.

Findings

Stronger magnetic braking with steeper density profiles.

Rotation decreases by about 50% when density slope increases from 0.2 to 1.8.

Magnetic field toroidal components grow with density steepness.

Abstract

The phenomenon of magnetic braking is one of the significant physical effects of the magnetic field in rotating molecular clouds. The physical characteristics of the core can affect on the core rotation rate. and one of the important parameter is the core density structure. According to observation, by regarding the power-law density distribution, $r^{-p}$, for molecular cloud cores, using smoothed particle hydrodynamics simulation, the results show that the increasing of density steepness (i.e., larger $p$) leads to the intensity of the toroidal components of the magnetic field and as a result larger $B_{\phi}$-components lead to more transfer of angular momentum to the outward. Thus, results show that the magnetic braking being stronger with increasing density slope in non-uniform molecular core. For example, the rotation of the system can approximately decrease by fifty percent from $p=0.2$ to $p=1.8$ for a non-uniform system.